Anatomical interbody implant and gripper for same

ABSTRACT

The invention relates to an intersomatic implant designed to be inserted in the disk space defined between two adjacent vertebrae, namely an overlying vertebra and an underlying vertebra, for the purpose of reestablishing the anatomic space between the vertebrae, the implant being in the form of a cage ( 1 ) that is generally in the shape of a rectangular block having at least two sagittal walls ( 2, 3 ) interconnected at least by an anterior transverse wall ( 4 ) and by a posterior transverse wall ( 5 ), the walls ( 2  to  5 ) presenting rims ( 1 0) extending on one surface to define a first transverse face ( 8 ) and on the other side to define a second transverse face ( 9 ). According to the invention, the implant comprises: 
         a first transverse face ( 8 ) presenting in the sagittal plane a convex profile congruent with the sagittal anatomic profile of an overlying vertebra; and a second transverse face presenting in the frontal plane a convex profile congruent with the frontal anatomic profile of an overlying vertebra.

TECHNICAL FIELD

The present invention relates to an intersomatic implant for insertioninto the disk space defined between two adjacent vertebrae, in order torestore an appropriate height between the vertebrae and in order toallow bone fusion to take place between said adjacent vertebrae.

More precisely, the invention provides an intersomatic implant of thecervical type, for insertion into the disk space defined between twoadjacent cervical vertebrae.

PRIOR ART

In the state of the art, it is known to insert an intersomatic implantinto the disk space between defined between two adjacent cervicalvertebrae. Numerous embodiments of such intersomatic implants areproposed in the prior art. For example, a known cervical intersomaticimplant is in the form of a cage comprising two sagittal wallsinterconnected by a anterior transverse wall and by a posteriortransverse wall. Between them, the walls define an open volume forreceiving a bone-filler substance for encouraging bone fusion betweenthe two vertebrae.

In general, it can be assumed that inserting an implant of theabove-described type into the disk space between two adjacent vertebraeis liable to lead to the vertebrae being incorrectly positioned relativeto each other. This means that it is not possible to obtain good bonereconstitution between the vertebrae concerned.

The invention thus seeks to remedy the above-specified drawbacks byproposing an intersomatic implant adapted to comply better with theanatomy of the spinal column.

SUMMARY OF THE INVENTION

To achieve such an object, the intersomatic implant is designed to beinserted into the disk space defined between two adjacent vertebrae,namely an overlying vertebra and an underlying vertebra, for the purposeof reestablishing the anatomic space between the vertebrae, the implantbeing in the form of a cage that is generally in the shape of arectangular block having at least two sagittal walls substantiallyparallel to a sagittal plane and interconnected at least by an anteriortransverse wall and by a posterior transverse wall extendingsubstantially parallel to a frontal plane, the walls defining betweenthem an open volume for bone filler and presenting rims extending on onesurface to define a first transverse face and on the opposite surface todefine a second transverse face.

According to the invention, the implant comprises:

-   -   a first transverse face presenting in the sagittal plane a        convex profile congruent with the sagittal anatomic profile of        an overlying vertebra; and    -   a second transverse face presenting in the frontal plane a        convex profile congruent with the frontal anatomic profile of an        overlying vertebra.

The invention also seeks to provide an instrument for manipulating sucha cage, enabling the drawbacks of known manipulation instruments to beremedied. It is known to provide two holes in the anterior wall of acage so as to enable two fingers presented by a manipulation instrumentto be engaged therein. Unfortunately, while the instrument ismanipulating the cage, there is a risk of the cage becoming separatedfrom the instrument, and of it becoming impossible to withdraw theimplant after it has been put into place.

Another object of the invention is thus to provide an instrument formanipulating a cage in the general sense, regardless of whether it iscervical and/or lumbar, and adapted to hold the implant safely andreliably while it is being put into place or repositioned.

To achieve such an object, the manipulation instrument of the inventionis a forceps for an implant in the form of a cage generally in the shapeof a rectangular block comprising at least two sagittal wallssubstantially parallel to a sagittal plane and interconnected at leastby an anterior transverse wall and by a posterior transverse wallsubstantially parallel to a frontal plane, the cage being provided withtwo housings extending substantially facing each other in a frontaldirection substantially perpendicularly to the sagittal plane of thecage, the forceps having two branches movable relative to each other andeach provided with an insert-engaging jaw.

According to the invention, each jaw is provided with a radial studextending in line with the other radial stud and suitable for beingmoved towards the other stud so as to be engaged in a respective housingformed in the implant.

Various other characteristics appear from the following descriptiongiven with reference to the accompanying drawings which show embodimentsand implementations of the invention as non-limiting examples.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an embodiment of an implant inaccordance with the invention.

FIG. 2 is a front view of an implant seen substantially along arrows f₂of FIG. 1.

FIG. 3 is a sagittal view of an implant seen substantially along arrowf₃ of FIG. 1.

FIG. 4 is a plan view of a forceps for manipulating an implant inaccordance with the invention.

FIGS. 5 and 6 are views on a larger scale respectively from above andfrom the side showing the implant-engaging jaws of the forceps shown inFIG. 4.

FIG. 7 is a perspective view showing an intersomatic implant supportedby a manipulation forceps in accordance with the invention.

BEST METHOD OF IMPLEMENTING THE INVENTION

As can be seen more precisely in FIGS. 1 to 3, an intersomatic implantin accordance with the invention is in the form of a cage 1 which isgenerally in the form of a rectangular block and is designed to beinserted in the disk space between two adjacent vertebrae, e.g. cervicalvertebrae. The cage 1 has a first sagittal wall 2 and a second sagittalwall 3 extending substantially parallel to each other and to a“sagittal” or “antero-posterior” plane S. The sagittal walls 2 and 3 areinterconnected by an “anterior” transverse wall 4 and by a “posterior”transverse wall 5 extending parallel to each other and to a frontalplane F extending perpendicularly to the sagittal plane S.

It should be observed that the cage 1 can have one or more intermediateor mid walls extending substantially parallel to the sagittal and/ortransverse walls. Preferably, connecting fillets 6 are provided betweenthe sagittal walls and the transverse walls firstly along their internalvertical faces and secondly along their external vertical faces so as toprovide a cage 1 having rounded corners on its external and internalvertical faces. For example, the walls 2 to 5 present substantially thesame thickness. Similarly, the height of the anterior transverse wall 4is greater than the height of the posterior transverse wall 5 (FIG. 3).

Internally, the cage 1 presents a volume 7 defined by the verticalinside faces of the walls 2 to 5 and designed to be filled with abone-filler substance for prompting intersomatic fusion. In the exampleshown, this volume 7 opens out into a first transverse face 8 that is ontop and into a second transverse face 9 that is at the bottom. The walls2 to 5 present, on one surface, rims 10 defining the top transverse face8, and on the opposite surface, rims 10′ defining the bottom transverseface 9.

The cage 1 has protuberances or projections 11 formed on the rims 10 and10′ of the walls 2 to 5 so as to enable the cage to bite into theunderlying and overlying vertebrae. In the preferred example shown, theprotuberances 11 are constituted by ridges extending parallel to oneanother and to the frontal plane F. Naturally, the protuberances can beof different shapes and could be implemented, for example, in the formof individual spikes or by ridges forming chevrons. In general, itshould be understood that the top and bottom transverse faces 8 and 9correspond to the envelope containing the tips of the protuberances 11.

According to a characteristic of the invention which is shown moreclearly in FIG. 3, the top transverse face 8 has a convex profile C₈ inthe sagittal plane S which is congruent with or complementary to thesagittal anatomic profile of an adjacent or overlying vertebra in theexample shown. It should be understood that the rims 10 of the walls andmore precisely the protuberances 11 defining said top transverse face 8are arranged to be inscribed in an envelope whose section in thesagittal plane S is rounded or convex in shape.

In a preferred embodiment, the top transverse face 8 is defined in thefrontal plane F by a straight or rectilinear profile C′₈ (FIG. 2). Therims 10 of the walls 2 to 5 defining the top transverse face 8 arepreferably arranged to be connected to the outside faces of the walls 2to 5 via connecting fillets 12.

According to another characteristic of the invention which can be seenmore clearly in FIG. 2, the bottom transverse face 9 presents a convexprofile C₉ in the frontal plane F, which profile is congruent with orcomplementary to the frontal anatomic profile of an adjacent orunderlying vertebra in the example shown. The rims 10′ of the walls 2 to5, and more precisely the protuberances 11 defining said transverse face9 are arranged to be inscribed in an envelope whose section in the planeS is of rounded shape.

Furthermore, it should be observed that the bottom transverse face 9presents a profile C′₉ in the sagittal plane that is substantiallystraight.

Advantageously, the above-described cage 1 is adapted to receive atleast one, and in the example shown two, radio-opaque markers 13incorporated over at least a portion of the height of the cage in theanterior and posterior transverse walls 4 and 5.

The above-described cage 1 is particularly adapted to enable it to bemanipulated by manipulation forceps 15 of the kind shown in FIGS. 4 to7, the forceps having two branches 16 each provided at one end with aninsert-engaging jaw 17.

The cage 1 has two housings 20 extending in line with each other andeach adapted to receive a radial stud 21 formed on each of the jaws 17of the forceps. In the example shown, the housings 20 are formed in thesagittal walls 2 and 3, being in alignment and extending in a frontaldirection perpendicular to the sagittal plane S. The housings 20 arepreferably located close to the anterior transverse wall 4. In theexample shown, each housing 20 opens out into the two opposite verticalfaces of the walls 2 and 3. Naturally, the housings 20 could be providedin the anterior transverse wall 4 extending in a frontal directionperpendicular to the sagittal plane S. In this embodiment, it can beobserved that the two housings 20 can be directly in communication witheach other so as to constitute a single bore. The transverse rightsection of each housing 20 is adapted to receive a radial stud 21, and,for example, is substantially elliptical in the example shown.

In a preferred embodiment, the cage 1 includes antirotation means 23 forco-operating with complementary means 24 provided on the jaws 17 of themanipulation forceps so as to prevent relative rotation between the cage1 and the forceps 15 when the forceps are engaging the insert. In theexample shown, these antirotation means 23 are constituted by a grooveformed in each sagittal wall 2, 3 to open out into a correspondinghousing 20 and extending therefrom to the outside face of the anteriortransverse walls 4. As shown more particularly in FIG. 3, each groove 23is substantially rectangular in right cross-section.

As can be seen more clearly in FIGS. 4 to 6, each insert-engaging jaw 17is arranged to present complementary antirotation means 24 in the formof an arm or a bar having a free end carrying a radial stud 21 lyingsubstantially in alignment with the other radial stud. Each arm 24 is ofcross-section complementary to that of the groove 23 and is designed tobe engaged at least in part in the groove 23 formed in a sagittal wallwhen each of the studs 21 is engaged in a complementary housing 20.According to a preferred characteristic of the invention, when the studs21 are engaged in the housings 20 (FIG. 7), the outside faces of thejaws 17, i.e. the arms 24, extend substantially in line with the outsidefaces of the sagittal walls 2 and 3 so as to limit the approach pathrequired for installing the cage.

Engaging the studs 21 in the housings 20 ensures that the cage is heldsecurely and prevented from moving in translation, and the co-operationbetween the arms 24 and the grooves 23 prevents the cage from moving inrotation, in particular in a frontal direction. This ensures that thecage is completely prevented from moving relative to the jaws 17. Itshould be observed that the antirotation means 23, 24 could beimplemented in a different manner. For example, the housings 20 could beprismatic in shape for co-operating with studs of complementary shape.

According to a preferred characteristic, each jaw 17 is provided with astop abutment 27 for coming into contact with the external face of theanterior transverse wall 4 of the cage when the studs 21 are engaged inthe housings 20 so as to transmit forces that are exerted axially on theforceps. As can be seen more precisely in FIG. 4 to 6, each stopabutment 27 extends radially substantially parallel to the adjacent stud21 which is connected to the stop abutment 27 via the locking arm 24.Each stop abutment 27 is preferably arranged on the jaw 17 so as to comeinto contact with the external face of the anterior wall of the cagesubstantially in line with the sagittal walls 2 and 3. Such adisposition provides the advantage of enabling pressure forces exertedon the end 30 of the forceps where the branches 16 join to betransmitted in such a manner as to facilitate insertion of the cagebetween the vertebrae. The branches 16 of the forceps are preferablymade so as to be resilient and urge the jaws 17 permanently towards eachother. In this respect, moving the branches 16 towards each other causesthe jaws 17 to move apart because the branches cross over, whereasreleasing the branches 16 automatically causes the jaws 17 to movetowards each other.

SUSCEPTIBILITY OF INDUSTRIAL APPLICATION

The above-described cage 1 is particularly adapted to complying with thedisk space defined between two vertebrae, e.g. cervical vertebrae.Complying with the anatomy of the intervertebral disk that is replacedby the cage 1 serves to encourage bone fusion between the vertebrae andto restore the static configuration of the spine. Furthermore, the cage1 is made particularly simple to put into place by using themanipulation forceps 15 of the invention. Thus, from an anteriorapproach path to the cervical spine, resection is performed on theosteophytes, the disk is removed, and then the plane faces of thevertebrae are revivified. Thereafter, a cage 1 can be taken hold of bythe forceps 15 by acting on the branches 16 to move the jaws 17 apart,then positioning the studs 21 in the housings 20, and then by acting onthe branches so that the jaws 17 move towards each other, causing thestuds 21 to penetrate into the housings 20 and causing the arms 24 topenetrate into the grooves 23. It should be observed that the grooves 23are capable of providing a guidance function for the studs 21 which arethus brought up to the housings for insertion purposes. In thisposition, the cage 1 is held completely securely relative to the forcepsby the studs 21 being engaged in the housings 20 and by the arms 24being engaged in the grooves 23, and also by the abutments 27 cominginto contact against the anterior transverse wall 4. The cage 1 can beinserted into the disk space, with it being possible to apply thrustforce to the end 30 of the forceps, should that be necessary. Pressingthe branches 16 together to move the jaws 17 apart enables the studs 21to be disengaged from the housings 20 so as to allow the forceps to bewithdrawn.

The invention is not limited to the examples described and shown sincenumerous modifications can be made thereto without going beyond theambit of the invention.

1. Manipulation forceps for an implant, the implant being in the form ofa cage that is generally in the shape of a rectangular block-having atleast two sagittal walls substantially parallel to a sagittal plane andinterconnected at least by an anterior transverse wall and by aposterior transverse wall substantially parallel to a frontal plane, thecage being provided with two housings extending substantially facingeach other in a frontal direction substantially perpendicularly to thesagittal plane of the cage, the forceps comprising two branches movablerelative to each other and each provided with an insert-engaging jaw,each jaw being provided with a radial stud extending in line with theother radial stud and suitable for being moved towards the other stud soas to be engaged in a respective housing formed in the implant. 2.Manipulation forceps according to claim 1, wherein the jaws are arrangedto present antirotation means complementary to means provided on thecage so as to enable the cage to be prevented from moving relative tothe forceps.
 3. Manipulation forceps according to claim 2, wherein eachjaw includes, as its complementary antirotation means, an arm which isprovided at its end with a radial stud and which is designed to beengaged, at least in part, in a groove formed in a sagittal wall andextending from the housing to the external face of the anterior wall. 4.Manipulation forceps according to claim 1, wherein each jaw is providedwith a stop abutment for coming into contact against the external faceof the anterior transverse wall of the cage when the studs are engagedin the housings so as to transmit forces exerted on the forceps. 5.Manipulation forceps according to claim 4, wherein each stop abutment isarranged on a jaw so as to come into contact with the external face ofthe anterior transverse wall of the cage substantially in line with thesagittal walls.
 6. Manipulation forceps according to claim 1, whereinthe jaws are urged towards each other by the branches.